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The present invention relates to aerosol dispensing devices, and in particular to valve assemblies that provide automatic dispensing of aerosol content at predetermined time intervals, without requiring the use of electrical power.
Aerosol cans dispense a variety of ingredients. Typically, an active is mixed with a propellant which may be gaseous, liquid or a mixture of both (e.g. a propane/butane mix; carbon dioxide), and the mixture is stored under pressure in the aerosol can. The active mixture is then sprayed by pushing down/sideways on an activator button at the top of the can that controls a release valve. For purposes of this application, the term xe2x80x9cchemicalxe2x80x9d is used to mean liquid, liquid/gas, and/or gas content of the container (regardless of whether in emulsion state, single homogeneous phase, or multiple phase).
The pressure on the button is typically supplied by finger pressure. However, for fragrances, deodorizers, insecticides, and certain other actives which are sprayed directly into the air, it is sometimes desirable to periodically refresh the concentration of active in the air. While this can be done manually, there are situations where this is inconvenient. For example, when an insect repellant is being sprayed to protect a room overnight (instead of using a burnable mosquito coil), the consumer will not want to wake up in the middle of the night just to manually spray more repellant.
There a number of prior art systems for automatically distributing actives into the air at intermittent times. Most of these rely in some way on electrical power to activate or control the dispensing. Where electric power is required, the cost of the dispenser can be unnecessarily increased. Moreover, for some applications power requirements are so high that battery power is impractical. Where that is the case, the device can only be used where linkage to conventional power sources is possible.
Other systems discharge active intermittently and automatically from an aerosol can, without using electrical power. For example, U.S. Pat. No. 4,077,542 relies on a biased diaphragm to control bursts of aerosol gas at periodic intervals. See also U.S. Pat. Nos. 3,477,613 and 3,658,209.
However, biased diaphragm systems have suffered from reliability problems (e.g. clogging, leakage, uneven delivery). Moreover, they sometimes do not securely attach to the aerosol can.
Moreover, the cost of some prior intermittent spray control systems makes it impractical to provide them as single use/throw away products. For some applications, consumers may prefer a throw away product.
Thus, a need still exists for improved, inexpensive automated aerosol dispensers that do not require electrical power.
In one aspect the invention provides a valve assembly that is suitable to dispense a chemical from an aerosol container. It is of the type that can automatically iterate between an accumulation phase where the chemical is received from the container, and a spray phase where the received chemical is automatically dispensed at intervals.
There is a housing mountable on an aerosol container, a movable diaphragm associated with the housing which is linked to a leg, the diaphragm being biased towards a first configuration, an accumulation chamber inside the housing for providing variable pressure against the diaphragm, a passageway in the housing suitable for linking an interior portion of the aerosol container with the accumulation chamber, and a valve stem positioned in the housing which the leg can ride along.
When the diaphragm is in the first configuration, the valve assembly can prevent spray of the chemical from the valve assembly. When the pressure of chemical inside the accumulation chamber exceeds a specified threshold, the diaphragm can move to a second configuration where chemical is permitted to spray from the valve assembly.
In a preferred form a barrier is provided in the passageway to regulate the flow of chemical through the passageway. There is a textured surface on at least one of the barrier and a wall of the passageway facing the barrier to provide a leak of chemical therebetween even when the barrier contacts the facing wall. This can enable some temperature compensation as the pressure of the gas increases. In this regard, when room temperature rises, the pressure of the gas in the can rises. This will press the barrier more firmly against the passageway, slightly crushing the textured surface (e.g. molded polypropylene) so that the leak flow is automatically adjusted to not increase as much with the increased temperature.
A porous material is disposed within the passageway to regulate the flow rate of chemical there through, the diaphragm is positioned on an upper wall of the housing, and the diaphragm will shift back to the first configuration from the second configuration when pressure of the chemical in the accumulation chamber falls below a threshold amount.
The valve stem and the leg are preferably both axially movable. There may also be an actuator portion of the housing that rotates to cause chemical to be able to leave the container and enter the passageway.
In an especially desirable form, the accumulation chamber has a base that is sloped (preferably radially inwardly sloped) so as to direct liquid chemical that may collect in the accumulation chamber towards the pathway.
Methods for using these valve assemblies with aerosol containers are also disclosed.
The present invention achieves a secure mounting of a valve assembly on an aerosol can, yet provides an actuator that has two modes. In one mode the valve assembly is operationally disconnected from the actuator valve of the aerosol container (a mode suitable for shipment or long-term storage). Another mode operationally links the valve assembly to the aerosol container interior, and begins the cycle of periodic and automatic dispensing of chemical therefrom. Importantly, periodic operation is achieved without requiring the use of electrical power to motivate or control the valve.
The valve assembly has few parts, and is inexpensive to manufacture and assemble. Further, it is self-cleaning to help avoid clogs and/or inconsistent bursts. One aspect of the self-cleaning operation is that the barrier can move up and down as the device cycles so that the underside of the barrier pad, and then the top of the barrier pad are flushed as the pad cycles up and down to avoid residue accumulation. Another aspect of the self-cleaning operation is the axial movement of the leg along the valve stem. Again, residue accumulation is avoided.
The foregoing and other advantages of the invention will appear from the following description. In the description reference is made to the accompanying drawings which form a part thereof, and in which there is shown by way of illustration, and not limitation, preferred embodiments of the invention. Such embodiments do not necessarily represent the full scope of the invention, and reference must therefore be made to the claims herein for interpreting the scope of the invention.